Ok, I admit it, here
comes the cat o' nine tails.
I think that some clarification is needed. So-called repatination products
work different ways.
Dellars -- recreates natural copper tarnish -- this is the result of sulphur in the mix combining with the copper in the coin to create copper sulfide, which is the same stuff that is created on copper cents (in US at least) as a natural result of circulation. This is also exactly what happens to silver coins when they "tone" -- it is a sulfide. In the natural process of tarnishing, the sulfur
comes from almost anything that touches the coin --
hands, clothes, or even the atmosphere. Because this is a natural process, you can leave a copper/bronze coin that has been stripped shiny new to naturally tarnish by leaving it exposed to sulfur bearing compounds (air polution is probably the best), so leaving the coin on the window sill for a couple of years works. Dellar's just works faster. Apparently you could do the same by exposing the coins to hydrogen sulfide gas, but that is seriously above my experience level.
This, though is
not patina.
Patina is what forms on the surface
after natural tarnish. First, copper carbonates forms. Then through oxidation, the copper is coated with verdigris, which is a mixture of copper acetate and copper carbonate. Then, finally,
patina forms, which can include copper sulfate, cuprous oxide, and/or any mix of the two, along with substances -- like dirt -- that surround the coin. See "Cleaning and Preservation of Coins and Medals", Sanford Durst, for details of this process on many different
types of coin metals.
To the best of my knowledge, there is nothing -- no process, no dip, no coating -- that recreates actual
patina. Either you recreate tarnish (via Dellars or time) or you
re-color the coin using something like Jax or, in the case above, using shoe polish. These products "assign" a color to the surface of the coin that is not, strictly speaking, warranted. There is absolutely nothing "natural" about these products. Yes, the coin looks better when it is done. But fundamentally, there is no difference between "dyeing" the coin this way or by painting it!
Except, of course, that painting a coin would be probably be considered by most collectors to be deceitful. It is certainly more time consuming that dragging old
Constantine through a tin of Kiwi. But at the end of the day, the shoe polish trick is probably
fine on our own private
collections, though they will, someday, re-enter the market (hopefully many, many years from now!). I just know that if I bought a coin from that "well known ancient coin specialist" and found out the color
had been imparted by shoe polish, I'd be one hot puppy. Like most things, if something "unnatural" has been
applied to the coin, a sellar should declare such at time of sale. If everything is above board,
fine, no hard done. If no warning is given, I think it is fradulent and deceitful. IMHO
I do ask the boards, though, where the line gets drawn? Someone like Scott, who has significant artistic skills, could probably paint a
patina on a coin that would probably fool all but an expert. But is that right? Is is right to use shoe polish or some other "repatination" product to re-color a coin? Incidentally, don't include Dellars in that mix because it doesn't recolor the coin -- it re-creates a naturally occuring tarnish.
Anyway, the shoe polish thing does, at least, protect the bronze from further corrosion and
bronze disease, so it provides value from that perspective (darn it, now I'm wondering what a cordovan polish would do to shiny brass...).
Congius -- that's an interesting tip on the STPP -- I'd like to learn more about it. Thanks.
So much for an opposing gush... More opinions?
Mark
